Method of manufacturing spark plugs



I A. B. SCHUPP.

METHOD OF MANUFACTURING SPARK PLUGS Flled July 21 1928 March 25, 1930. fig

Patented Mar. .1930 I UNITED STATES PATEN r OFFICE ALFRED 1B. SCHUPP, OF RICHMOND HILL, NEW YORK, ASSIGNOR, BY MESNE ASSIGN- MENTS, TO MOTO METER GAUGE & EQUIPMENT CORPORATION, OF LONG ISLAND CITY, NEW YORK, CORPORATION OF DELAWARE METHOD OF MANUFACTURING SPARK PLUGS Application filed July 21,

5 of uniform and accurate widths will be facilitated.

- It is obviously desirable in any spark plug that the electrode terminals be set apart a distance which experience has determined to be best for the operating conditions for which the plug is designed. In the case of spark plugs of the motometer type which have a variable gap, itis particularly desirable that the initial gap setting be accurate, as otherwise the final gap may be too large, thus causing the cylinder to miss, or if the initial gap be too small the spark will be too feeble, particularly .at lower temperatures'. In accordance with my present invention I pro ose to make the gaps narrower than the nal gap desired without taking pains that such narrowed gaps are of any accurate predetermined value. I then interpose amoving, grinding surface of predetermined thickness equal preferably to the width of the gap desired, thus grinding away one of the terminals the necessary amount.

The invention will be best'underst'ood by reference to the following detailed descri tion taken with the annexed drawing 1n which: 7 r

Figure 1 shows, in perspective, the opera-' "tion of my improved method;

Figure 2 is a viewin elevation seen from the right of Figure 1; and

Figure 3 is a view of employed. In Figure 1, A denotesthe spark plug having-a central electrode 10 and an electrode 11 generagiv which is of thermostatic metal and arranged so as to produce a wider gap when the cylinder is hot. 3

In the manufacture of the spark plug in accordance with the present invention, the gap is set at some value smaller than thede sired one; but withoutany attempt at precisidn being made. A grinding element, forming part of a grinding mechanism denoted by'B, isthereafter interposed and operat between saidelectrodes with the rea grinding element 1628. Serial No. 294,445.

sult that the material of the electrode next to the grinding surface of the disk is quickly ground away and a gap of the desired size is produced.

As indicated, grinding element B consists of a rotatable spindle 12 carrying a disk'13 having one surface thereof formed of abrasive material of suitable type. Disk 13 is removably held on said spindle-by means of a holding screw 14, it beingnoted that disk 13 has an aperture 15 of non-circular shape which fits theend of the spindle 12 of corresponding shape. Preferably the width of said disk 13 is substantially that of the desired width of gap so that the grinding element may be interposed between the electrodes and quickly withdrawn, whereupon the correct gap will be formed automatically. As shown, the disk 13 is preferably covered with the abrasive material on one side only, the other side being smooth, although'if desired both sides may be so covered. However, it is usually desirable to have the grinding take place on the electrode other than the central electrode as the size of the latter is necessarily limited, and therefore the use of a disk having abrasive on one side only is preferred.

In this manner, an easy, quick, and accurate method is provided for insuring that the spark plugs are manufactured of uniform spark gap. At the same time the need for precision in manufacture and in assembly of the parts is substantially reduced so that rejec-. tions .of parts are less frequent, and production is'speeded.

The grinding of the gap has the further advantage that the sparking surfaces are made clean and bright.

Various changes may be made from th method above described in detail without departing from the spirit of the invention.

I claim: t

1. In the manufacture of spark plugs, the method of forming a gap of uniform Width between the electrode terminals which consists in originally forming the gap of less width than that desired, providing a rotary grinding element equal in thickness to the final width of gap desired, and operating said element between the electrodes'to cut the gap to the desired width.

2. The method according to claim 1, in

which the grinding is confined substantially to one of the electrodes.

3. The method according to claim 1, in which the grinding is confined substantially to the non-central electrode.

- In testimony whereof I. have afiixed my signature to this specification.

. ALF. B. SCHUPP. 

